DESCRIPTION (Adapted from author's abstract): Tissue invasion by the dimorphic fungal pathogen Candida albicans is associated with the proliferation of hyphal forms of the organism. Although this suggests that this morphological form is responsible for pathogenesis, countermanding data suggest that the hyphal form is not intrinsic to disease, but rather, coincidentally expressed invasive factors mediate invasion. A developmentally regulated protein Hwp1p was identified which mediates adherence to buccal epithelial cells and is required for virulence in a mouse model of systemic disease. Expression of the gene HWP1 is highly regulated. The corresponding mRNA is undetectable in cells growing as yeast and abundant in the hyphal form of the organism. Differential transcription of the gene is the most likely mechanism controlling developmental expression. This leads to the hypothesis that flanking regions of the gene contain cis-acting regulatory elements whose interaction with DNA-binding proteins serves to regulate HWP1 mRNA levels. An extension of this hypothesis is that the regulatory proteins controlling HWP1 expression are part of a regulatory circuit controlling expression of other developmentally expressed genes. The specific aims of the proposed project are to 1, verify differential transcription of HWP1 using GFP (green fluorescent protein) as a reporter, 2., identify cis-acting elements controlling expression, 3., identify, clone and mutate the binding proteins that interact with these cis-elements and 4., identify global regulatory networks by isolating genes that are co-regulated with HWP1. Defining the molecular mechanisms controlling expression of this adhesin and identifying co-regulated genes may have long-term medical benefits in facilitating the development of alternative therapies.